At least 65 people have been killed during clashes in Cairo, Egypt's health ministry said, after violence erupted at a demonstration in support of ousted president Mohamed Morsi.

The ministry said nine others died in violence in Egypt's second city Alexandria, putting the toll in two days of unrest at 74.

The Cairo bloodshed is the worst since Mr Morsi was ousted in a military-led coup on July 3 and prompted domestic and international condemnation, as protesters accused security forces of using live ammunition.

Ahmed Aref, a spokesman for Morsi's Muslim Brotherhood, said 66 people were killed at Cairo's Rabaa al-Adawiya mosque where supporters of the ousted president have been camped since July 3 to demand his reinstatement.

An AFP correspondent counted 37 bodies in an Islamist-run field hospital at the mosque, and the emergency services said other hospitals received an additional 29 corpses.

Mr Morsi's supporters said security forces had opened fire on unarmed protesters, but Egypt's interior ministry insisted security forces used only tear gas, and blamed the clashes on Islamists.

Witnesses say security forces used live rounds

State media and the interior ministry said police fired tear gas at stone-throwing protesters on the airport road, but witnesses said security forces fired live bullets.

By midday, medical workers began ferrying bodies wrapped in white shrouds to hospitals, carrying them on blood-soaked stretchers past a furious throng of Morsi loyalists.

Some wept and women ululated defiantly as each body was taken from the makeshift morgue in a marble-floored section of the mosque.

Rival protests were also held on Friday in Alexandria, where nine people were killed.

The health ministry said 748 people had been injured on Friday and Saturday, including 269 at Rabaa al-Adawiya.

The Cairo violence prompted condemnation from Sheikh Ahmed al-Tayyeb, the grand imam at Al-Azhar, the top Sunni Muslim authority based in Cairo.

He called for an "urgent judicial investigation" and punishment of those responsible, "regardless of their affiliation".

Egypt's vice-president Mohamed ElBaradei, who joined the transitional government that took over after Morsi's ouster, also condemned what he termed the "excessive use of force".

British foreign secretary William Hague urged "Egyptian authorities to respect the right of peaceful protest, to cease the use of violence against protesters, including live fire, and to hold to account those responsible".

And the EU called for "a rapid move to an inclusive transformation process" that would include the Muslim Brotherhood.

Security forces 'did not use more than tear gas': interior ministry

Spokesman Hany Abdel Latif insisted that police "did not use more than tear gas" and accused Islamists of firing on the security forces, wounding 14 policemen, two of them in the head.

Mr Ibrahim said security forces would act to disperse the pro-Morsi demonstrations "in a legal fashion" and "as soon as possible".

Security forces would seek to ensure "the minimum losses possible", he said, expressing hope that Morsi loyalists would "come to their senses" and go home.

The bloodshed came hours after army chief General Abdel Fattah al-Sisi, who led the coup that ousted Mr Morsi, called for a mass show of support for a crackdown on "terrorism".

Hundreds of thousands of anti-Morsi protesters obliged, thronging Cairo's Tahrir Square and around the Ittihadiya presidential palace on Friday.

But Morsi supporters said their turnout showed many "reject the bloody, military fascist coup that wants to set the wheel of history back".

On Friday, authorities remanded Morsi in custody for 15 days, accusing him of the "premeditated murder of some prisoners, officers and soldiers" when he broke out of prison during the 2011 uprising that toppled veteran strongman Hosni Mubarak, state news agency MENA said.

He also stands accused of conspiring to "storm prisons and destroy them... allowing prisoners to escape, including himself".

The military has so far kept Mr Morsi's whereabouts secret to avoid attracting protests by his supporters.

Egypt, the Arab world's most populous country, has been rocked by violence that has now killed some 300 people in the less than four weeks since the coup.

Political polarisation has raised fears of prolonged violence, and even a militant backlash, including in the Sinai Peninsula bordering Israel, where the army is already facing daily attacks.